text:
Why are most runways made of asphalt and not concrete?
From the little I know about vehicles in cities, nowadays concrete is preferred to asphalt for road construction as, while initially more expensive, concrete is supposed to be cheaper to maintain.
From a recent reading I understand India also uses asphalt in most places.
I have two questions:

Why haven't airports switched to concrete?
How can I check online the type of material used for passenger commercial airports around the world, especially transit hubs?

Many runways are indeed made of concrete. Larger airports such as Charlotte, Louisville, Sea-Tac, etc., use concrete. Perhaps cost is controlling at the smaller fields that use asphalt. I don't know.

I've never counted, but there are quite a few (at least in the western US) where the surface is dirt or grass.  There are many others where the asphalt surface apparently was laid down decades ago, and not renewed since.  For larger commercial airports (and many highways) an asphalt surface can be laid over a worn concrete base much more cheaply (and quickly) than redoing concrete from scratch.

@casey It seems to depend where you are in the world. The major airports in the UK, for example, mostly have asphalt runways -- Manchester and Glasgow Prestwick were the only ones I could find with any concrete or partially concrete runways. Schiphol, CDG and Barcelona are also asphalt; Frankfurt has two asphalt and two concrete; Munich and Zuerich are concrete. This is going by Wikipedia; I sometimes wonder if editors there confuse asphalt (which is often given as the material but is never actually used), asphalt concrete (which most people call "asphalt") and concrete.

Concrete certainly isn't preferred for road construction in the UK -- we built some concrete highways in the 1970s and everybody hated them because of the road noise. There are still a few stretches left but, when they do need to be resurfaced, they're replaced with asphalt. Concrete is more useful in hotter climates.

I believe (but could easily be wrong) that Poland has a significant fraction of concrete roads.

I would say asphalt gives better friction. Is porous, so it can also drain when raining.

Concrete it is very loud and especially on hot days it can even break up. Happened in summer 2009 and 2013 on some german "Autobahns", extremly dangerous. Furthermore you have to maintain the gaps between the concrete plates (keep clean, not to big not the small). Asphalt instead can get some holes, if there is a crack in the surface or the underground but that can be fixed.

This description of a new runway in Brisbane shows some of the differences between concrete taxiways and asphalt runways, although it doesn't describe the reason.

My first reaction to this question was that your assertion of "most" was untrue. Nearly all major airports (airline traffic) use concrete runways.
However, according to the Asphalt Pavement Alliance, some 85%+ of general aviation airports use asphalt, and they claim some majors as well. They claim that asphalt is more cost-effective and takes less time to lay down than concrete. So for those airports, where long-term budgets might not be guaranteed, it likely makes sense.

"Nearly all major airports (airline traffic) use concrete runways." This is not the case. Heathrow, Gatwick, Schiphol, Charles de Gaulle, Dubai, Narita, Kansai, Bangkok Suvarnabhumi all have only asphalt runways, according to Wikipedia. And that wasn't me cherry-picking -- those were literally the first eight major non-US airports I thought of, except for the couple of European airports with concrete runways that I mentioned in my comment to the question

nowadays concrete is preferred to asphalt for road construction as, while initially more expensive, concrete is supposed to be cheaper to maintain

You may find some disagreement from anyone who's actually driven on concrete roads...
Concrete as a surface is certainly more resilient to traffic in the short term.  However the resulting road surface is significantly less smooth.  This is very noticeable for European visitors to the US, where concrete is more widely used for road surfaces.  In the UK, some sections of motorway were built in concrete in the 1960s, and these are universally unpopular with drivers.  To my knowledge, roads in the UK at least are no longer built in concrete for this reason.  It perhaps is less of an issue in the US due to the very soft suspension which is standard on US vehicles.
Concrete is also very much harder to repair when it develops holes, and those holes tend to be deeper and sharper-edged.  Even after repairs, the resulting road surface will never be fully even.  This makes concrete less suitable for roads which experience freeze-thaw conditions, namely most of Europe and the northern US.  Concrete also has issues with thermal expansion, which makes it less suitable for places which experience high daytime temperatures (or at least this needs to be considered during construction).
As ymb1 says, you can put asphalt over concrete though, which gives you the best of both worlds.

Well, he did say for road construction without specifying who prefered it. The preferences of designers and construction crews don't implicitly match the preferences of motorists. :)

In most cases, major aerodrome runway pavements are originally constructed using concrete (PCCP).  Improvements (resurfacing,strengthening, etc.) on an operational runway are undertaken during off-peak hours (maybe nighttime) to avoid airport disruptions especially if an airport has a single runway configuration. But because of the necessity of runway improvement, asphalt concrete are utilized.
Newly laid asphalt may be used immediately after the asphalt curing time. Unlike concrete which cures in the first few days of paving, new asphalt may be allowed to aircraft operations as soon as it is compacted and cool.
The runways you have observed may be originally constructed using concrete but resurfaced using asphalt.

Asphalt or concrete decisions on FAA sponsored projects are made on life-cycle cost analysis. Sometimes one wins out over the other, but neither is inherently better.


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What are the current principles for turbofan nacelle air path design?
The Wikipedia entry for 'turbofan' states:

Some high bypass ratio civil turbofans use an extremely low area ratio (less than 1.01), convergent-divergent, nozzle on the bypass...

But the article doesn't give supplemental references or other background apart from working line control. Can anybody give some more information if this is the case for a lot of nacelles being built nowadays or that the majority of turbofan cowls are 'simply' converging ducts and whether or not there is a trend to go to condi-nozzles in the future?

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How does a turboprop engine work?
I don't understand how it works, can someone provide me with details?

Welcome. What don't you understand in the turboprop? Basically a turboprop is a turbojet with a gearbox. See this question

If you're surprised by how turboprops work wait until you learn what the M1A1 Abrams tank use for an engine (spoiler: it's also a turbine engine just like turbojets and turboprops)

Come now, does the proposed duplicate actually provide details of how a turboprop engine works? I don't see how that is an "exact duplicate".

I agree with @JonathanWalters. I did vote to close, because the question is unclear, not because it's a duplicate. So the OP should try to explain what he/she already knows (e.g. how a turbojet works -- else start by searching/asking about the turbojet, not the turboprop) and explain what he/she is missing (e.g. the free turbine in the PT6).

The following describes reverse-flow, free-turbine type gas turbine engines such as the Pratt & Whitney Canada PT6 series of turbo-prop engines that I am familiar with. There are also geared turboprop engines such as the Garrett models; I am not very familiar with these.
The Beechcraft systems description for one of the PT6 models provides the following:

The PT6 engine has a three stage axial, single stage
  centrifugal compressor, driven by a single stage reaction
  turbine. The power turbine, counter-rotating with the compressor turbine, drives the output shaft. Both the compressor turbine and the power
  turbine are located in the approximate center of the engine
  with their shafts extending in opposite directions. Being a
  reverse flow engine, the ram air supply enters the lower
  portion of the nacelle and is drawn in through the aft
  protective screens. The air is then routed into the
  compressor. After it is compressed, it is forced into the
  combustion chamber, and mixed with fuel that is
  sprayed in through nozzles mounted around the gas
  generator case. Two spark igniter plugs are used to start combustion. After
  combustion, the exhaust passes through the compressor
  turbine and two stages of power turbine and is routed through
  two exhaust ports near the front of the engine. A fuel control system schedules fuel flow to maintain the power
  set by the gas generator power lever. Propeller speed within
  the governing range remains constant at any selected
  propeller control lever position through the action of a
  propeller governor, except in the beta range where the
  maximum propeller speed is controlled by the pneumatic
  section of the propeller governor.
The accessory drive at the aft end of the engine provides
  power to drive the fuel pumps, fuel control, the oil pumps, the starter-generator,
  and the tachometer transmitter.
The reduction gearbox forward of the power turbine provides
  gearing for the propeller and drives the propeller tachometer
  transmitter, the propeller overspeed governor, and the
  propeller governor.

The following diagram depicts airflow through the compressor stages, the combustion chamber, the power turbines, and the exhaust section. The propeller bolts on the front of the engine at the output shaft (left side in the diagram).

The following diagram depicts the various compressor and turbine stages. Note the physical disconnect between the gas generator and power generator turbines. This is why these types of engines are called "free-turbines": the power turbine (and by extension the propellor) can spin freely from the gas generator section.

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What happens if Solar Impulse II encounters un-expected head wind and runs out of battery power?
I noticed that battery charge level dropped to fair levels in some occasions in this article. It dropped to around 20% at the end of day 5 before morning of day 6.
To what extent will a flight be affected by unexpected strong head wind that results in lower Eastward ground speed and delaying time to next sun shine and battery runs out?

I tend to think weather prediction is quite good nowadays, what is the plan if this happens on long ocean flight? Does the ocean have thermals where a glider can stay up 'forever' while waiting for morning sunshine?
On Solar Impulse, or similar 'experimental' (at the edge of limits) flights, like the solo circumnavigation balloon flight, do they usually have a 'chaser/spotter' plane flying along?

Related

Leg 7 of this flight was originally planned to go from Nanjing, China to Hawaii. The flight diverted to the alternate airport in Nagoya, Japan, due to expected bad weather on what would have been the fifth day of the flight. Every leg of the flight was planned with careful attention to the weather, so that such a situation could not arise.

In the worst case, the pilot could bail out and (almost did once on a Solar Impulse 1 flight)  and allow the plane to ditch itself. Finally, the plane was only flown in the summer, when days were longer.

Solar Impulse has two means to store energy: Batteries and altitude. Weather permitting, both will be fully charged at sunset, and mostly depleted over the night. The rate of depletion at sunrise depends only on the time between sunset and sunrise, not on the direction and strength of the wind.
Headwind only means that less ground is covered. Solar Impulse is optimized to fly at a certain speed and will not fly much faster or slower, regardless of wind. If the wind is strong enough, it will simply not cover any ground but be blown back. But the wind will not cause the batteries to be depleted earlier, and the next day they will be recharged if the sky is clear.
Wind speed and direction vary with altitude, so the aircraft might well overcome a wind that had prevented it to make any progress the night before by flying at a different altitude the next day. After all, flight duration is limited by the pilot, not the power source.

Further information lookup up shows that the Sun approaches SI2 at speed of 1668km per hour at equator. "If the wind is strong enough, it will simply not cover any ground or even be blown back" but Eastward ground speed has little delay effect on when SI2 will see next morning sun ray and begin charging.  Favorable Eastward ground speed enables seeing next sunshine just a little sooner.

@EEd: Change in longitude is so insignificant that I let it out of the answer. Of course you are right, there is an effect, but it is small - for SI2, nights are of approximate equal length, not least because it only flies in favorable weather.

If the battery level goes to low, due to poor planning or an bad weather forecast (winds end up less favorable than forecast) then solar impulse doesn't make it to its destination.  If they are over water they crash into the water.
Look, solar impulse is a totally impractical aircraft, built to give the two pilots some records.  Everything about the aircraft is impractical and dangerous.  There isn't enough power for a decent climb rate or cruise speed. Even a quite common low altitude headwind would be enough to have the aircraft flying backwards. There isn't enough energy storage for sufficient range to safely go any reasonable distance.  The structure had to be built extremely light weight so the aircraft is fragile (can't take much turbulence).  And there is no way to overcome these limitations with further development.
The maximum solar power reaching earth is about 1kw/sqM, and this is only achieved in clear sky's, when the solar cells are directly facing the sun.  Since there is no way to have the solar cells face the sun on an aircraft (the cells have to be flush with the airframe) this means that most of the day you will get even less than 1 kw/sqM (half of the day you will get zero).
To put this in perspective this would mean a light aircraft, like a Cessna 172, would receive a maximum power of 10-15kw of solar energy over the entire airframe.  In reality, using very expensive cells with the best efficiency available, the actual energy collected would be more like 3-5kw.  A Cessna 172 is a very low powered, low performance aircraft but even still, it gets about 120kw of power from its little 4 cylinder Lycoming engine.  The 3-5 kW of electricity that a solar Cessna 172 could collect in the most favorable conditions wouldn't be nearly enough to keep the airplane in the sky.  And again, this comparison is not about trying to make a solar powered commuter airliner or something of similar performance, there isn't enough sun for even the lowest performing human carrying aircraft.

There seems to be a fair amount of unnecessary editorializing in this answer.  Everything past the first paragraph is only tangential to actually answering the OPs question.  If you could edit this answer to stick a little closer to the topic at hand, it would be appreciated.  We try to keep answers here as succinct as possible.

Glider distance record is 3000km with 0 battery energy storage and 0kW engine. Solar Impulse has more in common with a glider than a Cessna.

In my humble opinion, Solar Impulse 2, and many similar projects, now and countless generations before us, are excellent demonstration of human’s desire to excel, ability to plan, organize and execute, and vast accumulation of knowledge, science, technology and engineering.

Progress in 'each step' may be small but they add up over time.  George Boole likely did not see Boolean algebra and logic form the basis of many machinery, automation and modern computer. https://en.wikipedia.org/wiki/Boolean_algebra#Computers


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How can coefficient of lift on the ground with flaps in the takeoff position be calculated using airfoil data?
In essence I'm working on a design project and I'm specifically looking at takeoff analysis at the moment. I already have access to great textbook resources, but I'm struggling to determine the coefficient of lift $(C_{L_G})$ on the ground with flaps in take-off position for the following equation taken from Appendix K-4 of Synthesis of Subsonic Airplane Design by Torenbeek:
$$\frac{a}{g} = \frac{T}{W} - \mu - \left(C_{D_G} - \mu C_{L_G}\right) \frac{\frac{1}{2}\rho V^2 S}{W}$$
Similar equations can be found in other textbooks, but I haven't found any reference to how $C_{L_G}$ can be determined from airfoil data. Currently I'm considering just using the zero geometric angle (ie compensating for the AoA the wing is mounted at) coefficient of lift for the airfoil, but how would I then account for the position of the flaps?

Thanks for the comment! There are rough adjustments available to turn airfoil data into whole aircraft curves (e.g. adjust gradient based on aspect ratio, wetted surface area/reference surface area) that I had planned to use. The geometric angle of attack, which is pretty much the incidence angle you refer to, is what I had planned to use but would I need to make any additional corrections?

There is quite a lot written on the topic, especially as part of "ground effect" vehicles research.
For example, Cui and Zhang cite two different types of lift coefficient. The first one (simpler and given here) is based on flat plate airfoils and is a modification to the well-known
$\frac{dC_l}{d\alpha}=2\pi$:
$$C_L=2\pi\alpha(1+\delta^2)(1-2\zeta)$$
with
$$\zeta=\frac{\sin\alpha}{4(h/c)}$$
and
$$\delta=\frac{\cos\alpha}{4(h/c)}$$
In the above expressions, $h$ is the height of the wing above the surface (ground, water, etc.), $c$ is the chord and $\alpha$ is the angle of attack.
I strongly recommend you check out "ground effect"/"Ekranoplan" literature - should be useful.

there must be a typo in your answer. Is the second or third equation for $\delta$ or $\zeta$?

Edited! Thanks!

The question is asking a principal analysis of aircraft aerodynamics. The aircraft is a 3-dimensional object, and 2D airfoil calculations or data ($C_l$) can be used to approximately define the 3D coefficients ($C_L$).
The main methodology is the wing-strip approach. This is simple to comprehend and simple to put into calculations (excel, code, etc).
Basically the wing is divided span wise into several sections. Each section is assumed to have a constant chord, so the 2d data is quite useful to define the force at this section. After combining all forces, one can conclude the total force and then conclude the calculations by non-dimensionalizing the total force.
In helicopter rotors the same methodology is named as blade element model.
There's also literature on approximating the flap effects using empirical formulas, if you do not wish to analyze different foil geometries using CFD. Refer to ESDU, DATCOM, or other references, or Hoerner's "lift" book, for these empirical approaches.


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Do "water bomber" aircraft pilots have more relaxed rules?
I have no exposure to aviation regulations, but I'm curious if some rules are different for emergency aircraft pilots.  Similar to ambulance drivers and police officers being allowed to speed or run red lights for the sake of emergencies.
Specifically, this video shows a water bomber very close the ground and bystanders during an approach:

My gut tells me two things:
A) that this plane is dangerously close to the ground, and
B) that this would be a serious incident, representing some sort of strike against the pilot's record.
Please correct me if I'm wrong about either point.  If either are true, though, is the situation treated differently for emergency pilots?  Are they trained to go that close to the ground, like police officers are trained to handle a car at higher speeds?  And are their rules different for that reason?

I'm not sure how much the answer would vary country to country, aircraft to aircraft, or even situation to situation.  So if the question is too broad, assume the United States or Canada even though that's not where the video is from, and assume a water bomber pilot in a situation just like this.

Maybe something went wrong? This looks more like a narrowly avoided crash.

@h22, that's what I thought.  Is that the sort of thing a pilot might need to report?

@mins The article is in French too...Oh look, some new French words for me.

@mins Thank you for the context.  Seems that park was closed to the public.  Even if the people were not there, though, it's a big problem for the plane to come that close to the embankment, right?

That was entirely intentional. He's reloading with water and to do that he needs to come in very low and skim the lake surface. Nothing wrong here, just a pilot who knows what he's doing.

While picking up water is a normal operation, that plane almost just hit those people (and the ground). See the people ducking in fear under the shadow of the fuselage? Count me out on that - on the ground or in the plane!

I agree this seems too low. That may be the result of a wind shear while stabilizing the aircraft before scooping, or a piloting mistake.

I agree it's low, but the camera perspective makes it look worse than it is

That doesn't look like a perspective problem to me...

I'm reminded of the approach to RAF Waddington in Lincolnshire, England.  The runway threshold is very close to a public road.  There are warning signs and lights, and an official viewing area, but that doesn't stop people standing right under the approach.
Every so often they get a closer encounter than they were expecting:
https://www.youtube.com/watch?v=vvoM1B9LbtI

my gut feeling tells me it's photoshopped or perspective is playing tricks on the eye (or maybe both).

@jwenting, the image is just a still taken from the video I linked, it is not photoshopped.  Also, the cyclist is in the shade because of the shadow cast by the plane directly above and in front of him. That plane is real and is as close to the ground as it looks.

All aircrews have to comply with laws and regulations, unless they have a waiver that makes them exempt for certain regulations. Aerial Fire Fighting need to fly lower than the minimum safety altitude in order to pick up water, so they will have a written permanent waiver to do so.
This is similar to ATO's conducting training for student pilots. They can be allowed to fly below the minimum safety altitude (in Germany: 500ft) for the purpose of training engine failures and attempted emergency landings in fields.

In all honesty, it does not look like recklessness to me, it looks like the pilot miscalculated his approach and came in too low and with not enough speed, as he bounces off the water surfaces instead of doing a proper flare.

No, law enforcement and fire department aircraft have to comply with all of the same safety guidelines that regular aircraft do. If this had taken place at a controlled airport, the crew would most likely be disciplined, but since it was outside of an airport and no damage or injury occurred, it's likely nothing will happen.
What they did was reckless, but as long as they caused no damage to their aircraft or to anyone on the ground there is nothing to punish them for. At an airport they could be punished for deviating from procedure, but otherwise nothing. (This is according to FAA guidelines, not sure what the DGAC guidelines are.)

Thanks for the answer!  Follow up question: "since it was outside of an airport and no damage or injury occurred, it's likely nothing will happen."  So does that mean the crew theoretically should be disciplined for being so close to the ground, but it just won't happen?

What they did was reckless, but as long as they caused no damage to their aircraft or to anyone on the ground there is nothing to punish them for. At an airport they could be punished for deviating from procedure, but otherwise nothing. (This is according to FAA guidelines, not sure what the DGAC guidelines are.)

That's clear and I believe it.  If you include the meat of comment in the answer, I'll accept it.

@ColinPierce I find it VERY VERY hard to believe that you have to physically damage something for them to be punished.

@Dan A similar situation would be and ambulance/firefighter truck overrunning a red light during an intervention. They are allowed to deviate from the general rule, and put themselves/other in dangerous situations. It is however widely accepted and, unless there is an accident, there are no consequences.

@Dan That being said, it is highly probable that they will be reprimanded, internally to the sécurité civile (organization handling water bombing in France) for not respecting their own procedure. But I can't imagine a legal action in this case.

If it was reckless (as defined by the law), it would be punished. However, I would argue it was not reckless, exactly in the same way that it is not reckless for ambulance to run red lights: they have to do it and have a waiver for it.

In the USA wild land fires are covered by "temporary flight restrictions" which restrict access by general aviation. Fire related flights set transponder code 1255 so ATC can identify them. This is to avoid midair collisions.
As for altitude, in the USA over sparsely populated areas and open water there is no low altitude restriction other than staying 500 feet from a building or boat.

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text:
What does prevent air and fuel to be mixed upstream of the compressor?
Why isn't fuel injected before the compressor or intake chamber?
The combustion chamber gets a lot of design and clever thinking to be able to mix fuel and compressed air in a short distance/space. This adds more weight and length to the overall engine.
I understand that changing that way of injecting fuel would need a new design and engineering to make it happen, e.g. to prevent blade corrosion, but nevertheless, could it be done?
If someone or a company did it already, and it didn't work, what were the reasons?

Suck-Squeeze-Bang-Blow, if you inject before the squeeze, you may have problems with proper fuel atomization.

@RonBeyer I don't think the question is about four-stroke piston engines.

In the original Brayton engine, a piston compressed a volume of pre-mixed air and gas...

@DavidRicherby I'm not talking about one either, the process is the same for jet engines and two-stoke engines too. in a jet engine the fan sucks, the compressor squeezes, the igniter bangs, and the exhaust blows.

“if you inject before the squeeze, you may have problems with proper fuel atomization”, except that's precisely what spark-ignited (gasoline) engines do!

tl;dr The flame would progress upstream into the compressor until it and damage it, fatally disrupt the carefully balanced flow and stall the engine, or both.
long answer: In a turbine engine, there is a continuous flame where injected fuel is ignited by the already burning fuel downstream. Now you can't match the flow speed and the flame propagation speed exactly, because a small disruption could then blow out the engine and because both depend on the power setting in non-trivial way.
So in normal operation, the flame can propagate upstream until it gets to the point where the fuel is not yet sufficiently mixed with air to burn and there it stays. If you injected the fuel before the compressor, the flame would progress into it and as it would engulf the last stage, it would damage it and it would also increase the pressure beyond what the preceding stages could maintain, which would stall the compressor and cause the engine to stop, either immediately due to lack of oxygen, or by causing more damage with each stall cycle.
Note that spark-ignition (gasoline and LPG and CNG) engines usually do inject fuel before compression, but it limits their compression ratio to around 12:1 with high-octane gasoline, 14:1 with clever tricks. If the compression ratio was higher, the fuel-air mixture would ignite from the compression heat before the piston reaches the top-dead-centre and act against the rotation. In contrast compression-ignition (Diesel) engines have compression ratio at least 14:1 and inject the fuel only when it should start burning.
While early turbines had rather low compression ratios, the newest generation is getting into the range comparable with Diesel engines where the fuel might ignite due to the compression heat alone—they still use sparks for ignition, because the starter won't build up as high pressures in them, but it clearly shows they can't inject the fuel before it should start burning.

Interesting... In the original Brayton gas engine, that worked at constant pressure too, but with pistons, a stack of wire screens was necessary to prevent the propagation of the flame from the burning charge back to the 'receiver', that was full of a mixture of air and gas...

@xxavier, I didn't know that, but it confirms the explanation. A fine wire mesh does stop flame propagation, but it would also cause significant resistance to the air flow. Not injecting the fuel before the point it should start burning is way simpler.


text:
What are the typical lift, lift coefficient and drag coefficient for a A320 in cruise?
What would you expect the typical lift force and coefficient of lift and drag to be for a A320 at cruise?
Considering flight at 36,000 ft, mass approximately 72 tons, velocity 230 m/s with a surface area of 122.6 m² and density 0.366 kg/m³.
The results I've calculated seem a little high, CL=0.666 and L=724 kN

In s/l flight, weight and lift are practically equal, so  –if those are metric tons– the lift will be 72000 x 9,8 = 705600 N. Now, concerning the CL, we may solve for CL the expression for lift:
$C_L = \frac{2 · L}{\rho V^2  S } $
$C_L = \frac{2\cdot9.8\cdot72000} { 0.366 · 230^2 · 122.6 }$
$C_L = 0.595$
Now, assuming a L/D of 15, the CD = 0,594/15 = 0,039

DeltaLima, I used newtons... Concerning the '2', perhaps I forgot to put it, but the end calculation was right...

You're right. It was my mistake, if only when writing the answer down... Thanks...

Firstly, thanks you for your reply. It's starting to become more clear now. From my CFD analysis, my modelled wing (only starboard hand) generates 369,000n of lift, which seems more plausible if the entire airframe is producing approximately 705600n. My model of course omits the flap cowlings and engine, so I'd expect the lift to be slightly higher.


text:
Can an airline reject a passenger for being overweight?
I have a Cessna 172S and despite having 4 seats in the cabin, I cannot take 3 more passengers besides myself as the pilot with a full tank of fuel due to safety in weight balance issues.  As the pilot, I'm 100 lbs overweight.  Hypothetically, we can imagine a situation where a small regional carrier using a turboprop can have only one seat left but the length chord from center of gravity for that seat may cause an unsafe weight balance for the aircraft loading if the passenger is very overweight.
In that case, if not other solution can be found, could the airline reject to passenger for the motive of their weight?

United Airlines has a simple solution.

Does a company have to serve everyone? They should be able to refuse to sell without stating a reason. Just like you can refuse to sign a contract with someone. Of course, if you already have a ticket (i.e. already signed a contract) things get difficult …

@Michael: "They should be able to refuse to sell without stating a reason". Not in my country, this would be illegal. There must be a legitimate ground.

@mins: Auto-translate of your link: “The refusal of a consumer to sell a product or to provide a service is prohibited except for a legitimate reason” But what is a legitimate reason? I’ve been refused entrance in more than one club/restaurant for “hygienic reasons” because I was barefoot … is this a legitimate reason? I think you could easily make up a reason if you needed one. The aircraft passenger being obese (and thus likely to endanger other passengers and him/herself) certainly sounds like a legitimate reason though. Sorry for starting a discussion here.

Even where you were allowed to refuse service "for any reason, or no reason at all", discrimination is still illegal. There is a laundry list of categories which are considered discrimination.  The burden of proof is largely on the customer, but companies are caught all the time.

@Michael: I answered you initial comment which stated no reason had to be provided (I said this would be illegal in some countries), now your second comment is about the improper reasons that are given, I think we are in agreement. For night-clubs in France, they found a bypass: Clubs are private associations, and there is no relationship seller-customer, so this article doesn't apply. Still as @ Harper mentioned, you may try to fight the refusal on other causes. It's like for employment. Physical characteristics are not allowed for any discrimination at exactly the same level than religion.

@Michael> the validity of the given reason would be assessed at the trial, if the would-be client sues. So… if you are causing enough inconvenience that the client is likely to sue, you'd better have a solid reason. Even more so if there are witnesses. Alternately you could just not care and pay the compensation the courts decides. They tend not to be very high in France.

@Koyovis: That is....?

@Zaibis This method.

@Michael neither of your examples are legitimate reasons, but both are sadly not uncommon. And quite often people just make up rules out of thin air to find justification for their own prejudices.

@Michael: I would assume "to prevent the airplane from potentially crashing" would be quite the legitimate reason indeed...

Yes.  If carriage of said person on a particular flight would cause the aircraft to be overloaded or outside of its CG envelope, the airline has full right to refuse them passage for safety reasons. It would be illegal under Part 121 and Part 135 to do otherwise.
Practically speaking though, most large commercial aircraft have such great payloads that this would not happen on a frequent basis.  Now the airlines may charge said person for an additional seat costs because of their size and girth.

Can they refuse the NEXT passenger, or are they expected to do something like hold a lottery, as United allegedly did?    Who gets cut, the person who was last through the jetway, or the one who was issued a boarding pass last?  Policies?

@mongo each airline will have a policy, usually either a lottery like UA did, or first come first serve principle so the last people to either buy tickets or check in get refused. Either method ensures the operator can't be sued for discrimination because the passenger refused was black, a woman, or whatever "protected group".

Airlines have rejected passengers for their size, perhaps more than their weight, specifically for being unable to fit into a passenger seat.
There appears to be some debate as to whether this practice is legal. "Customer of Size" is a politically correct industry term.
For example, the written policy at United Airlines requires a passenger to purchase an additional seat, if the armrests cannot be put down and stay down, regardless of whether a family member is seated adjacently.  US Air's policy was to attempt to accommodate a customer of size, when there is additional seating on the plane.
Should this be a potential issue, travelers should contact the airline in question, as policies may change without publication.

Well it is a bit of a practical problem isn't it. I'm sure United Airlines has a solution...

When the aircraft is going to be overweight, then yes, the airline can only take what weight the performance numbers will support.  That's somewhat uncommon, but it can defintely happen when takeoff performance is limited (hot day, short runway, full airplane, etc) or when the landing weight will be at the maximum allowed landing weight (full airplane + significant fuel load required at landing due to requirements for an alternate airport, for instance).  (More on this topic and how the numbers work in this answer.)
As far as a passenger being overweight, that's less likely to be an issue, simply because most airlines (in the US, certainly -- this may apply less in other countries) use an average weight multiplied by the number of passengers, rather than weighing each passenger individually.  While the difference between four ballerinas and four linebackers in a C-172 is very significant, that same difference among 100+ passengers on a commercial airliner just evens out over everybody else onboard.  So there isn't really a case where the airline would say, we can't take this passenger (weighing 300#) but we can take that passenger (weighing 100#), because we only have 250# of weight left.  Either you can take one more passenger, or you can't.  Doesn't matter what he/she weighs.

Do you have any sources for the average weight numbers? Several years ago, I've seen a claim saying that the average weights were calculated in 1930s and 1940s and are therefore not completely representative of modern values, but I'm not sure how reliable the claim is.

@AndrejaKo: Passenger weight survey by EASA/NEA in  2008-2009: Survey on standard weights of passengers and
baggage from this question.

He didn't ask about the overall weight, he asked about a balance problem.

@WGroleau The answer works the same regarding balance -- either the airline can put "a passenger" in this seat, or they can't. Not weighing passengers, there is no option where you could put "a light passenger" in the seat but not a heavy one. For weight & for balance both, every passenger is considered as weighing the average -- since unless it's a particular type of charter, actual weights are unknown anyway (at least for major U.S. airlines).

"..that same difference among 100+ passengers on a commercial airliner just evens out over everybody else onboard." Unless you have extreme cases like this. I hope in such cases there is someone that can do the math correctly before allowing the take off! :-)

aircraft have crashed because they were overloaded despite the load sheet suggesting they weren't. As a result the average weight per passenger and piece of luggage have been adjusted upwards, but are still below the actual averages. This affects especially commuter carriers.

@AndrejaKo: And for the FAA, last updated in 2005:

At least from what I've seen, most airlines will board the passenger.
If they have concerns about weight and balance, they'll typically deal with that by rearranging luggage or (if necessary) leaving some behind to be carried on a different flight.
When I lived in Colorado Springs CO (runway at 6187 feet elevation), this was fairly common if you were taking off on a hot afternoon. In one case I recall, they even removed most of the carry on luggage from the aircraft--but they still took nearly all the passengers. At least to the best of my recollection, the only passengers who were left behind were those who refused to part with their carry-on items.

http://www.aviationqueen.com/?p=2585

Vilma Soltesz [...] three airlines — Delta, Lufthansa and KLM — refused to let her board on flights from her vacation home in Hungary to her permanent home in New York City, allegedly because she was deemed too overweight (at 452 lbs.) to fly.

Mind you she was so overweight they had physical problems boarding her. It was not like the gate agent said "you are overweight, we won't carry you" but still.

The phrase "allegedly ... deemed 'too overweight to fly'" sounds to me like a journalist's over-simplification.  At that sort of weight, there could be any number of other issues that come up, such as safely securing the passenger in a seat in a manner that complies with the regulations.  If you need more space than any seat or row of seats can provide, then the choice is to do something unsafe & let the person fly, or re-engineer a seat/row in order to accommodate 1 individual, or else deny boarding. That not one but all 3 of these airlines said "no" is, IMHO, pretty telling.

Could she walk?

Nope, she was wheelchair bound and one of the problems were that the plastic wheelchairs at one of the airports have failed under her weight.

Since your question was more concerned with balance (weight distribution) than total weight, the point about safety still applies.  However, if it were actually an issue, I suspect they could reassign seats to put the big guy closer to the middle.
I recently heard a pilot announce that we would be a little late because they had to move some luggage around for better balance.

I shouldn't have packed that anvil!

Oh, YOU'RE responsible for the destruction of my bicycle!  Where do I send the repair bill?

They move luggage around mid-flight? Do the cabin crew do it or does a machine somehow move them around?

@Mehrdad They bank the plane sideways +/- 30° a few times to shuffle it just about right...

Obviously they did it before taking off.  If they did it mid-flight, it wouldn't have made us late.

@Stian Yttervik: Banking - uncoordinated, or else it won't help shift that baggage - when close to CG limits would not help to make the flight any safer...

In the U. S., ANY business has a right to refuse ANY consumer for ANY reason (with certain exceptions). However, due to business reasons, an airline will force you to purchase another seat. In the case of a small airline, they could put you on another flight. Discrimination against consumers by businesses is permitted by law in the U. S., albeit, it's not wise for business. The exception is disabled persons with service animals. And they must meet certain  criteria before service is refused to them.

Your first sentence appears to not reflect the number of bakers, clergy and caterers who, for example, refuse to handle gay marriages, and then get sued, loose state licenses, etc.

It ignores those numbers, simply because it was wrong for those suits to have been won by the gay couples. Those businesses are private entities. Exactly where in the bill of rights of the Constitution of the U.S. does it explicitly state that gays have a right to sue because a private business owner exercises his/her religious rights as well as right to refuse service (as given by federal law) to a gay. Had the business owners gone to the supreme court, I am positive the business owners would have been ruled in favor.

I would also like to add, that the aviation industry is a whole different ball game than baking a gay cake. In aviation, if you name it, the Federal Aviation Regulations nearly allows it all...a Pilot can kick you off a plane for nearly ANY reason. Even if you smell bad. Remember the asian doctor who got his butt kicked by airport police? Well, there are about 5-10 different laws that man broke enacted by the FAA

@PiGuy88 it sounds like you are stating a political positon, that's not the format on SE.  Discrimination most certainly is illegal in all the usual categories, those being the exceptions to "any or no reason".   Ironically, the one thing you recognized as illegal discrimination, isn't. ADA is about access and is not punitive.  However several states add "disability" to the discrimination list, and ADA compliance is their litmus test.

@harper, negative, I am not stating a political position. I know all about the ADA. A business under no circumstances can refuse service to a disabled person with a service animal for any reason unless certain criteria are met. rarely does this meeting happen. My comment to mongo was a position of morality based on the constitution. Not my political stance on the matter. In terms of federal laws, a business can refuse service for ANY reason to ANYONE with exception for their color, race, religion, nationality, or disability. Places of worship are generally exempt from those all the way.

So therefore, as i mentioned, the businesses could have sued on a federal supreme court level, and would have won because sexual orientation is NOT covered under federal laws. however, getting back to the original topic, there's many laws that justify an airline refusing service to prospective passengers. All of them refer to the safety of the flight, and it can be proven very easily and are hard to argue with.

@PiGuy88 The Supreme Court would likely vote it as discrimination due to the Commerce Clause in the Constitution. ref Heart of Atlanta Motel, Inc. v. United States

@harper, considering that the current federal laws only cover discrimination of color, race, religion, nationality, or disability, no they wouldn't. Flat plain and simple... That would be unless you either  consider the LGBT mindset one of a disability, in which it would be admitting that a person is not born gay (which you're not), but rather a psychological disorder...which would really upset the LGBT community...OR legislation was passed on a federal level, adding sexual orientation to the list... Which in itself would be illegal, because it tramples on people's 1st amendment rights.

This is just a political rant.  It's not realy an attempt to answer the question and is factually incorrect


text:
How are winds aloft forecasts derived in the USA?
This question pertains specifically to the US NWS FB Forecast Product.
Winds aloft forecasts, technically the "Wind and Temperature Aloft Forecast (FB)", are issued 4x daily, at 00, 06, 12, and 18z. At each of these 4 periods, 3 products are produced: a 6-hour, 12-hour, and 24-hour forecast. How are the forecasted values actually predicted?

I took a tour of my local NWS office and spoke to the aviation weather unit people. My 8yo daughter even got to help launch that day's weather balloon, and then we went inside and monitored the balloon's data as it ascended.

One of the data streams was the winds, which prompted me to ask: ok, so we know the winds right now for this location, but how does this knowledge allow you to forecast 24 hours into the future? And secondly, there are more FB locations that there are weather balloon sites, so how does that work?

Here is the answer:
Data from the balloons are just 1 of many factors entered into the weather forecasting computer models, and the FB products are actually the result of two different modeling systems. The first two products (the 6hr and 12hr forecasts) are generated by the Rapid Refresh (RAP) modeling system, and the third product (the 24hr forecast) is generated by the North American Mesoscale Forecast System (NAM) model.
Both models produce numerical forecast data on a grid, with each grid point being 13km apart in the RAP model and 12km in the NAM model, and each grid point containing 50 vertical data points up to the 10mb level. From these data points, each "FB Location" is interpolated (both horizontally and vertically) to the geographical location of the depicted airport, and the various forecast altitudes.
Additional reading:

FAA AC 00-45H Aviation Weather Services. (This document explains U.S. aviation weather products and services. It provides details when necessary for interpretation and to aid usage. Chapter 5.13 discusses the FB product)
NWS Instruction 10-812 Aviation Wind and Temperature Aloft Forecast. (This instruction provides guidance to NWS offices, outlining preparation and format of wind and temperature aloft forecasts in support of commercial and general aviation. It also lists each location where a forecast is provided)

Interesting Trivia:

All forecast locations correspond to an airport, except for 7 locations in the Gulf of Mexico, 1 location off the east coast of northern Florida, 5 locations in the Gulf of Alaska, and 1 location near the end of the Aleutian chain. These 14 additional forecast locations correspond to heavily traveled air routes.
The RAP model runs hourly, and provides forecast data 21 hours into the future.
The NAM model runs every 6 hours, and provides forecast data 84 hours into the future

This is a great answer.


text:
Is it legal for a balloon to land at a US international airport?
Assuming the winds directed a hot air balloon near a US international airport, and the pilot has no other choice than landing, say near the runways/taxiways, would they face legal trouble/fines?

Probably yes for operating within a Class-B without a transponder and two-way radio contact with ATC. If they did have a transponder, and a radio, they would be in communication already. ATC probably wouldn't be happy, but they would probably accommodate.

The definition of "international airport" can be misleading. It just means that it is a port of entry. Many are in Class C and a few are Class D. Since Class B requires a clearance which is unlikely for a free balloon, the pilot would likely be in trouble. At smaller airports where only the transponder and two-way comm is required, maybe-maybe not. During the annual Albuquerque Balloon Fiesta balloons occasionally end up landing at KABQ. ATC deals with it and the FAA will investigate the circumstances. The bigger mistake is landing inside the Sandia Labs nuclear storage area.

See for instance the Reno Balloon races, where the balloons are launched from a park about 5 miles northeast of the airport, and generally drift across the approach to 16L/R, if not the airport itself.  Don't know if balloons have ever actually landed on the airport itself, but it would not surprise me.

@jamesqf: How do you race a hot-air balloon?

@Sean: While I'm no expert, I understand that you control the altitude of the balloon in order to take advantage of different winds at different heights.  See e.g. http://www.hotairballooning.com/race.php

places like ABQ and others where there are folks that fly regularly the airport is quite familiar with balloon traffic.  As well as the lack of landing spots in the city, the airport is the first open space if stuck over the city.  While illegal, if you need to land (usually you are out of fuel by then) then you can, there is a procedure to get your equipment back, no doubt you may spend the day explaining your actions and hoping for forgiveness.

during ballooning events ABQ or other, the airport is quite aware of that event some will send representatives to the pilot briefing, or either way the event organizers will provide phone numbers for the crew to contact the airport and there will be procedures for recovering the balloon as well as the obvious, dont land on the runways.

Assuming the winds directed a hot air balloon near a US international
  airport

By this I assume you mean a major airport in class B or C (possibly even D) airspace. An "international" airport is simply one that is an airport of entry and maintains customs officials and processing ability and may or may not be a "large/major" airport.

would they face legal trouble/fines

This depends on how the balloon is equipped. As mentioned in the comments you need a transponder and a 2 way radio to enter certain controlled airspaces (usually those surrounding big airports) and if the balloon is properly equipped it would be allowed to enter and utilize public resources such as airports and landing areas. This advisory circular on ballooning would indicate it is legal to enter all airspaces in a balloon.
There are of course some practical problems here such as the fact that as a balloon you can't really divert around an airspace if you are not granted clearance. If there is no safe landing space and the wind is blowing such that your only option is to enter the class B you may be stuck declaring an emergency, or at least getting back on the radio and explain whats going on. Some FAA officials may consider this poor/dangerous flight planning (since you should have looked at the wind prior to departure) and you may end up in some trouble for that.
From the Balloon Hand Book

As a general rule, balloons do not freely operate within Class B
  airspace. Equipment requirements are the same as for Class C airspace;
  however, due to air traffic congestion, the balloon pilot requesting
  entry to Class B airspace will likely be denied entry, as ballooning
  operations inside the Class B airspace constitute a potential traffic
  conflict....

But legally you can and the FAA prefers you coordinate before hand,

Should it become necessary for operational reasons to fly through
  Class B airspace, that flight should be coordinated at least one hour
  prior, as provided for by 14 CFR section
  91.215. It is permissible, and perfectly legal, to operate a balloon under the lateral limits of the Class B airspace.

Same applies for class C,

Balloon operations in Class C airspace, while technically feasible,
  are usually not advisable

What you are describing sounds like an emergency. In an emergency a pilot can take any reasonable actions necessary to ensure the safety of aircraft and occupants.
As others have mentioned there might be some other reasons for legal action, but since your question only refers to the landing of a balloon at an international airport, I will assume no other regulations were violated.
So, if no other regulations were violated up to the point that the balloon pilot had "no other choice" but to land at an international airport, then I would argue that the pilot could avoid (legal trouble/fines) either with a clearance from the tower(unlikely), or a declaration of an emergency.

A balloonist always has a choice of when he can land. He must carry enough fuel on board to remain aloft until a safe landing area can be reached. There is no way a busy control tower would allow him to land in the middle of the airfield. He might be granted clearance to fly through the control zone but would never be given clearance to land. If he was out of fuel, he would declare an emergency and accept the consequences. (Legal trouble/fines)


text:
Can a wing be stalled at a speed larger than its stall speed?
I was told pulling the yoke quickly and all the way back stalls the plane immediately. I believe this is not possible as long as this occurs above the stall speed.
I think about a styrofoam plane: Increasing the pitch angle (same effect as  pulling the joke) just makes the plane turn up with a small radius, but it doesn't stall.
Is this correct?
When I fly in straight line how can I provoke flow separation at wings above stall speed?

If you're talking about the cited stall speed in FCOM, turn off your anti-ice and go fly in the snow for a while, then you'll see how far wings can stall before hitting the stall speed. Not recommended though.

I'm not sure why you are so fixated on the "falling down" concept.  Stall occurs at a given angle-of-attack.  If the aircraft is "pulling G's" (i.e. creating lots of lift-- looping, turning, etc), this angle-of-attack can be reached at a much higher airspeed than it would occur in linear flight.  Yes, the flight path will not be a straight line in such a case.   So your observation "So when I fly in straight line how can I force flow separation at wings above stall speed? I think this is impossible." is true.  But it's kind of trivial as well.

So your observation "So when I fly in straight line how can I force flow separation at wings above stall speed? I think this is impossible." is true. But it's kind of trivial as well.  I think we all know that forcing an aircraft to enter an accelerated stall, will in most cases also force the flight path to curve away from a linear path.

It's kind of hard to tell what the actual question is here.  Is this the actual question?  "So when I fly in a straight line how can I force flow separation at wings above stall speed? ".  Maybe the answer is simply "you can't".

Unless perhaps you yank back so violently on the stick that you bring the wing almost instantly to an angle-of-attack where lift is near zero-- seems kind of implausible though

@quietflyer  "So when I fly in straight line how can I force flow separation at wings above stall speed? " yes this is question and you already answer it...my friend learn in school that you must be gentle with yoke/AoA becuase you can stall plan and he thinks if he pull yoke too hard plane will stall and "drop" IMMIDIATELY ..I think this is impossible

"I often hear "stall can happend at any airspeed"" -- "here plane is not stalled because of "hard yoke pull"" -- when flying at any speed,  just yank that yoke all the way back, as far as it can go, however much force it takes.  You'll probably stall.  And all your questions will be answered.  Can't guarantee a linear flight path though!

@JurgenM -- well, have you tried it?  And if not, why not?  Again, no one is saying that the resulting flight path will be a straight line-- but it's pretty clear that a stall will result, if you pull that yoke all the way back--

@quietflyer Because I dont fly. If I fly ,I will know answer...I think if you pull yoke as fast you can all the way back at any speed above "stall speed",plane will just turn up, going from straight path to curve up path...I think there is no way it will stall and go  immidietly down...Did you try it?

@JurgenM, I think your example of the stryofoam plane is hampering your understanding here.  Yes, a very small, very light airplane will simply arc abruptly upwards with a rapid increase in pitch.  But remember, the mass to surface area ratio increases dramatically as size goes up.  Larger airplanes have a lot more load on the wings, and more inertia to overcome when pitching.  They don't fly anything like your styrofoam model that just does a quick loop before striking you in the buttocks...

@JurgenM -- it might be helpful to google "snap roll" -- pertains to what happens when the stick is moved abruptly aft--

No, by definition.  Stall speed is the speed at which the wing stalls.  It's a variable that depends on loading, angle of attack, how the airfoil shape has been perturbed by icing, and many other factors.

Am voting to keep this question open. "Can a wing be stalled at a speed larger than its stall speed?" is a pretty clear question, and is has attracted a very good answer.

There are two linked questions top right, and I am certain that the subject of accelerated stalls has been covered in depth here, and on many searchable web sites. In fact, this is starting to read less like a question and answer, and more like a bunch of us trying to convince Jurgen to abandon a stubbornly held disbelief. I just don't know what else can be said on the subject...

@quiet flyer: "...ust yank that yoke all the way back, as far as it can go, however much force it takes..."  But can you do that without breaking part of the airplane?  The elevator cables, for instance, in which case stalling is going to be the least of your problems :-)

So when I fly in straight line how can I force flow separation at wings above stall speed? I think this is impossible.

Stall is a matter of angle, not speed
There is no stall speed, you can decrease speed or increase speed as long as you manage to remain below the stall angle.
Stall happens when the angle of attack exceeds the maximum angle of attack for the airfoil. So to stall you just need to increase pitch until the stall. This is how GA pilots train for stall prevention and recovery, see this video.
Let's take two examples:

In level flight, say at 60 kt, the stall angle of 15° is reached. Any attempt to climb by increasing the pitch will stall the wing and the aircraft will lose altitude (unless power is increased).

In steep descent, the speed is 200 kt, the pitch is quickly increased to level the aircraft, the angle of attack changes, say from -5° to 18°. The new angle of attack is larger than 15°, this immediately stalls the aircraft, even if the speed might be larger than 150 kt.

[My friend] thinks if he pulls the yoke all the way back as fast as possible, the plane will stall and immediately drop. I think this is impossible at speeds above stall-speed.

Your friend is right. This is the case of the last example. Again there is no stall speed, it's $\sf \color {orange} {\text {only}}$ a matter of angle of attack.
Reason for flow separation during stall

So flow separation is consequence of plane that "falling down" not initial reason why plane starts falling down.

No, flow separation is the consequence of air no able to follow the airfoil curve, because the angle between air direction and the curve is too high, so inertial effects are too strong compared to effects which make air following the surface. Inertial effects make air continue on its momentum instead of curving.
As air doesn't follow the airfoil curve, the pressure field is not able to create enough lift, and the aircraft loses altitude due to its weight. But losing altitude is not the cause of the flow detachment. To convince yourself, let's use a wind tunnel. The airfoil is fixed, so it cannot move down when lift decreases. From the linked video:

The airfoil is at the same location, but the flow has detached due to the angle of attack. The inertial forces won over the viscous forces, air now follows its momentum and eddies form:

So no vertical movement is required for stalling the airfoil.
Case of stall in level flight and apparent "stall speed"

Explain me why airflow stay attached at 61kts but separate at 60kts?

Again, this is not a matter of speed, but angle. You might be confused by the fact that if you want to fly level, and start decreasing the speed by decreasing the engine power, then the angle of attack must be increased. So:

You see an aircraft which speed is decreasing while the angle of attack is increasing.
At some speed value, the angle of attack will reach the stall angle, and the wing will stall.
We may call this speed the stall speed but this speed is valid only for flying level, while the angle is constant whatever the attitude. This is why we say there is no stall speed, but a stall angle.

If you try to stall the same wing in descent, the angle (the angle of attack, not the pitch angle) will be the same, but the speed will likely be much larger.
So instead of saying "the wing stalls at 60 kt, but at 61 kt is is still flying", you should say "the wing stalls at 15°, but at 14° it is still flying".
But actually the stall is not so abrupt.
Stall is not lift on/off, it's progressive
At some point the angle is too large, regardless of the speed, lift starts decreasing. Here is a typical lift coefficient vs. angle of attack curve:

Adapted from source
We see lift stops increasing with the angle of attack near 13°-15°. Then it decreases. This is the stall.
If the pilot just pitches the aircraft up, lift continues to decrease, and the aircraft loses altitude.
Can I climb while in the stall area?
Yes you can. That's not contradictory.
When the angle of attack is near the stall angle, the coefficient of lift is not 0, it is only decreased, if we continue to pitch up, it will continue to decrease, there is no possibility to increase it up (see the curve).
But the lift coefficient is not the only parameter when determining lift, velocity matters too, and even more than the lift coefficient Lift is proportional to $C_L$, but proportional to $V^2$:
$$L = \frac 1 2.C_L.A.\rho.V^2$$
($A$ is the wing area, $\rho$ is air density, two constant parameters).
So let say we're in a level flight at constant altitude (lift = weight). We reduce the power while increasing the angle of attack, so that our angle of attack is just at the beginning of the stall area. Obviously increasing the angle of attack will make the aircraft descend. But what happens if we can increase the power at the same time?

Let's say we pitch up a bit and the lift coefficient is reduced by 30% (e.g. it comes from 1.4 to 0.98).

Let's offset this reduction by an increase of velocity by 20% ($1.20^2\times 0.7 = 1$).

The result is L was multiplied by 0.7, then by 1.44, meaning it hasn't changed.

If we increase the velocity by 30% instead of 20%, then we starts climbing.
But let's not forget in the stall area of the curve,

lift coefficient decrease is large for a small additional angle of attack,
we won't be able to increase the velocity indefinitely,
maybe more crucial, we won't be able to increase velocity quickly enough, lift decrease will occur before the aircraft has accelerated, and if we try to maintain the altitude by a bit of additional pitch we might stall it for good.

Do I need lift at all?

I think about a styrofoam plane: Increasing the pitch angle (same effect as pulling the joke) just makes the plane turn up with a small radius, but it doesn't stall.

How do we gain altitude? By a force directed upward and larger than the weight. Lift is such a force, but it's not the only one.
For example a rocket has no wing, therefore doesn't produce lift, but the engines produce thrust. As long as thrust is larger than weight it's possible to ascend. Rockets have huge engines because they are heavy.
What about a styrofoam plane? It's very light, probably only a small force is required to make it gain altitude, therefore the propeller may be sufficient by itself to gain altitude if the airplane is pitched vertically. In that case it doesn't matter if the wings generate lift or are stalled. That's why you can exceed the stall angle, generate no lift and still can make the aircraft climb on its own momentum and the thrust provided by the propeller.
The wing in this case is used like the empennage, it just acts like a windvane and orient the fuselage. At this point, the aircraft doesn't fly anymore (flying means lift), it is propelled by the engine.
Stalling doesn't mean the aircraft must fall immediately. It falls only if there are no other forces but lift to oppose its weight.
Is it possible to actually reach the stall angle at high speed?
For many aircraft stalls are difficult to trigger at high speed because its actually difficult to reach the stall angle. This angle is about a 15° nose up relatively to the airflow (not to the horizon). At a large airspeed, the aircraft has enough momentum to climb when pitched up, and therefore it remains at a low angle of attack until the speed decreases and a stall at low speed is triggered.
A way to trigger a high-speed stall is to increase the load factor (g) e.g. by performing a steep turn.

For more details, see:

How does stall depend on angle of attack but not speed?

Comments are not for extended discussion; this conversation has been moved to chat.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Can a commercial pilot transport friends for free?
Is there anything in the FARs that would prohibit a commercial pilot from doing multiple trips to ferry friends to an event in his/her personal aircraft assuming that the friends did not provide any compensation?

When you say "no compensation" do you mean that the pilot pays all the costs?

If there is no compensation, even a private pilot can do this as much as they want. If the PIC is paying all expenses, they are not receiving anything of value from anyone except themselves.
"Logging hours is compensation" is true in the sense that it can be considered to be a form of compensation when the pilot is not paying all operating costs.
Note that compensation is not necessarily cash. The FAA interprets compensation very broadly. For instance, you may be in violation if you give flights to business partners with the reasonable expectation that you will receive more business from them in the future. This isn't a problem if you're flying friends, though.

compensation of any kind is irrelevant for the FAA here as the pilot has a CPL.  Whether the IRS wants to have a word is another matter entirely.

@jwenting A commercial pilot is forbidden from receiving compensation for carrying passengers under most circumstances unless they are operating under an air carrier certificate.

According to this interpretation that seems to match your scenario very closely, as long as you're also attending the event then a single trip is fine but multiple trips are not. And you would be acting as a private pilot, not a commercial pilot.
The interpretation was about an ATP who ferried fellow club members to an event (in nine flights!) and did receive money to cover costs, but the main points would apply to a CPL in your scenario too. In summary:

Flight time is compensation, therefore you're being compensated for the flights even if no money changes hands (the ATP argued that flight time in a C172 was worthless to him, but the FAA said they don't analyze individual cases)
Acting as a private pilot you can receive compensation only if a "bona fide common purpose" exists

If you aren't attending the event yourself, there's no common purpose
If you are attending the event, only the first flights there and back have a common purpose; subsequent flights to bring more people to the event do not

Acting as a commercial pilot you can receive compensation for transporting people only if you have an air carrier certificate (per 14 CFR 119.1)

You didn't give many details about your scenario, but if you're attending the event yourself then you should be fine for one flight each way under your private privileges. Any more than that and there's no common purpose.
Of course, the caveat here is that every situation is different and perhaps there's something about your case that would result in a different FAA interpretation. However, the basic points about compensation and common purpose are very consistent across interpretations.
(Apologies for not quoting the interpretation directly, but the FAA seems determined to make it as difficult as possible to copy and paste from their documents.)

I'd really like to see some evidence that this interpretation would be the same if there was no compensation. 'Common purpose' is applicable only if there is compensation, and the air carrier certificate applies only if there is compensation.

@DJClayworth The interpretation says "Generally, accrual of flight time is compensation and the FAA does not enter into a case-by-case analysis to determine whether the logging of flight time is of value to a particular pilot". So as I mentioned, the pilot is being compensated just by flying the aircraft, hence the need to prove a common purpose. And they rejected the ATP's argument that the flight time wasn't helpful for his career, so it seems unlikely that they would decide differently for a commercial pilot.

Are the passengers paying any of the costs? If there was I understand the issue. If not then where is the compensatiion? The pilot us receiving no compensation even in the form if flight time.

To follow your argument to its conclusion, if flight time is considered compensation even if the pilot is paying all the costs then why isn't he considered to be receiving compensation even if he does this without carrying passengers?

I'm with DJClayworth on this. And even if I weren't, the pilot is not under obligation to actually log his hours, thus removing that "flight time in itself is compensation" argument.

@DJClayworth The regulations say "carrying passengers or property for compensation or hire". If the pilot's alone in the aircraft, then there's no issue.

Too complex a discussion for comments. I still disagree and my downvote stands. If there has been a judgement or case where a pilot has paid all expenses and still been ruled to be carrying passengers illegally I'd be interested to see it edited into the answer.(The example you give specifically talks about 'shared expenses')

Flight time is only compensation if somebody else pays for it.  (or helps you pay for it)  If you are buying flight time, it isn't compensation.  Otherwise it would be illegal for any private pilot to ever fly!


text:
Control free and fixed static margin
For many aircraft root and tip chord is given but the exact location of aerodynamic center and center of gravity is not given. Considering this information;
How can I calculate control free and fixed static margin?

The stick-free static margin depends a lot on the elevator hinge moment coefficients of the aircraft. Depending on the sign of the hinge moment derivative with angle of attack ($c_{r_\alpha}$), the stick-free stability can be greater than the stick-fixed stability (greater for positive $c_{r_\alpha}$ because then the control surface will deflect into the changed airstream). By how much depends also on the derivative over deflection angle $c_{r_\eta}$, but this one should definitely stay in the negative range, or the stick will be hard to center.
The stick-fixed margin is much easier to calculate. If aspect ratio is reasonably high, the surface-weighted mean of the quarter points of all horizontal surfaces will give a good approximation of the neutral point $x_N$, and the center of gravity depends on the loading of the aircraft. Normally, you would calculate the margin for both the most forward and the most backward cg location $x_S$ for which the aircraft is certified.
With the given planform, the mean aerodynamic chord $l_\mu$ is also easy to calculate, and the stick-fixed margin is (x backwards positive): $$\frac{c_{M\alpha}}{c_{L\alpha}} = \frac{(x_S - x_N)}{l_\mu}$$

CG is never given as a fixed location because it changes with loading of the aircraft and other parameters. The control free neutral point is the CG location at which the control free pitch stiffness vanishes. That means that the control free point moves when the CG changes. The fixed static margin can be stick-free or stick-neutral and changes with CG, but also with elevator area.


text:
Why are my friends flying over Norway, Sweden and Denmark from Manchester to Vancouver?
I'll start off by letting you all know that I am 100% blind, so I won't be able to read a map.
My friend Hudson came over to Canada with her friends last year, September 1 or August 31, 2016.
She likes to check where she's at once in a while when flying. She said it was an Air Transat Airbus 330-200. She doesn't remember the flight number, but it was probably TSC-285 or TSC-255.
Anyway, when she flew from Manchester (EGCC) to Vancouver (CYVR), she said "(laughs), Ann was out like a light when we flew over the Scandinavian countries." How on earth does this work?  I may be blind, but I do know that Vancouver is southwest of Manchester, and the Scandinavian countries are northeast of Manchester.
My question is, why would they fly over Norway, Sweden and Denmark when that is the opposite way to Vancouver? I'd love for an explanation please.
Note:
If you explain the route i.e. "she went north over x, then headed west and flew over by y" that would help, though it's not a requirement.  It is guessing after all considering she may have taken off northeast or southeast from EGCC.

Yes she said they flew over the scandinavian countries while going form Manchester to Vancouver.

Are you sure she isn't including Iceland in that bin of "Scandanavian countries", or the fact that Greenland is run by Denmark?

Alls she said was the Scandanavian countries.  and why would she go over greenland or iceland? Vancouver is southwest of manchester, at around 49 degrees North lat while Manchester is about 53 degrees North.

As to Greenland & Iceland -- the answer has to do with great circles as we live on a round planet, not a flat pancake :)

She may have been referring to greenland or Iceland, still, would there be a doable route to Vancouver flying over Norway, Sweden or Denmark? and then there's still the track southwest from greenland, accross Canada and to the west coast.  (sorry if i'm being an idiot)

I edited the question so it gives you Hudson's exact words. (laughs) "Ann was out like a light when we flew over the Scandinavian countries"

She also said "'ad to wake the others up when we were over Alaska" so I knew she flew over Alaska, which is still too far north. or maybe I'm missing something. Perhaps if you kinda ran through the route i.e. she would have went norh twards x, then east twards Y).  I'm blind and can't read a map online, but doing something like (north twards x and east twards Y) wouldhelp me understand the great circle route she took better.

I'm guessing this is a while ago, since Air Transat only seems to fly Manchester-Vancouver in the summer? If it was within the last seven days, the flight number would be invaluable as we can then look on flightradar24.com to see the exact route the plane took.

@David Richerby it was like August 31 or September 1, 2016 and Hud saw her old flight record and she said it was air transat flight 285

@TheCat-alyst Ok -- that probably pins it down to just a couple of possible flights. It's possible somebody has a subscription to one of the flight-tracking sites that allows them to see flights from more than a week ago, so they'd be able to see exactly where the plane went.

@David Richerby I wish I had a subscription to flightaware or something like that.  I know that it was either august 31, 2016 or September 1, 2016 because Hud and the girls arrived in my home town the next day due to having to stay overnigh tin Vancouver.  Yeah, I think it may be tsc285, or at least the air transat flight from Manchester to Vancouver on either August 31, 2016  or September 1, 2016.  that should help.

Could also have been TSC 255. This flight appears representative of the MAN-YVR seasonal route. It did indeed go over Iceland, then Greenland, then Nunavut, Alberta, etc. The route was EGCC 5500N/11800W MERYT BOOTH LIONN1 CYVR. This is basically a straight (great circle) line from Manchester to Alberta.

@Michael Hampton ah, gotcha.  strange that HUdson said she was over the Scandinavian countries when Ann fell asleep.  Unless she was going by the fact that the vikings colonised those places, though that is srange. thanks though, you are amazing.

Well, technically Greenland is still a (largely autonomous) part of Denmark. So it's kind of sort of true... She might also have been mistaken.

@Michael Hampton fair point.  it's kinda fascenating to learn just where one would fly over when going somewhere, I'm hoping to go to Manchester myself in the near future.  Also had i not have lost my sight hwen I was 7, I'd probibly be training to be a commercial pilot right now, because I've always loved commercial aviation.

Sounds like you know more about geography than your sighted friends do.

@Tyler Durden i did my best to pay attention in geography class back in 2001. pluss I love traveling.


text:
How do investigators always know the logged flight time of the pilots?
Almost all incident investigation reports include the flight experience of the both pilots with hour accuracy. For instance, for MH370 just a few small fragments of the plane have ever been found, yet the investigators know the captain had 18,365 hours of flying experience. How do they know?
From that I have seen on a web, a pilot logbook looks like an unprotected paper document, often unlikely to survive. Do pilots actually keep the book at home or in the office, or maybe someone else apart the pilots logs the flight hours?

Hi h22, I recommend you deselect my answer and give the question a few hours. You may garner some better answers from more experienced folk that way

Statement reworded.

Accuracy vs Precision: the flying times are reported with precision to the hour or possibly tenth of an hour. That doesn't mean that the reported time is accurate to that same level. Might be, might not. The NTSB reports the best info they have, and if it's off by an hour or 5 or 10, well, that probably won't change the conclusions in the report anyway.

@Dan the accepted answers should be the first one that satisfy the op. The most upvoted one should be the best. You deserve it (unes factually wrong)

FWIW, the last commuter airline I flew for and the two 747 carriers I flew for furnished their pilots at the conclusion of a month with a detailed record of their flying. The only thing missing was how much of that time was IFR, which wasn't relevant because simulator check currency took care of that requirement. I stopped my personal logging and simply kept the company supplied logs. Obviously, in case of an accident, that company information would have been available to the FAA.

The methods that Dan referred to in his answer are valid, and might be used by investigators—the NTSB for example.
However, generally speaking the NTSB will not spend a great deal of effort researching pilot time. Instead they will resort to one of two methods of determining pilot experience.
Firstly, if a logbook is readily available—either found at the scene or made available through the investigation—it will be used to determine pilot experience.
Secondly, if a logbook is not readily available, the NTSB can determine pilot experience based on the pilot's reported flight time on his or her last application for a medical certificate. Since an application for a current FAA third class medical can be several years old, private pilot experience determined by this means may not accurately reflect an accident pilot's actual level of experience. However, a professional pilot's application for an FAA first or second class medical will only be six to twelve months old, and will much more accurately reflect that pilot's actual level of experience.
Similarly, FAA certificated pilots report their flight time on some IACRA applications for pilot certificates. This reported time will have been independently verified as accurate (unlike times reported on medical certificates). However, in most cases, a pilot will have applied for a medical more recently than for a certificate.
For actual examples of these two scenarios, see NTSB report CEN16FA333, in which both are detailed.
For the first pilot involved:

The [first] pilot's flight history was reconstructed using logbook documentation. His most recent pilot logbook entry was dated July 31, 2016, at which time he had accumulated 135.5 hours total flight time, of which 48.6 hours were listed as pilot-in-command. All of his flight time had been completed in a Cessna model 172N single-engine airplane. He had accumulated 5.0 hours in actual instrument meteorological conditions, 12.9 hours in simulated instrument meteorological conditions, and 3.4 hours at night. He had flown 24.7 hours during the prior 12 months, 4.4 hours in the previous 6 months, 2.4 hours during prior 90 days, and 1 hour in the 30 day period before the accident flight. The pilot's logbook did not contain any recorded flight time for the 24 hour period before the accident flight.

For the second pilot involved:

According to FAA records, the [second pilot], age 60, held a private pilot certificate with a single engine land airplane rating. His last aviation medical examination was completed on November 6, 2014, when he was issued a third-class medical certificate with a limitation for corrective lenses. A search of FAA records showed no previous accidents, incidents, or enforcement proceedings. A pilot logbook was not recovered during the on-scene investigation; however, on the application for his current medical certificate, he reported having accumulated 120 hours of flight experience.

You might also want to mention that pilots have to submit their hours in any IACRA application, so if the pilot did a recent checkride of any kind, that would be another fairly reliable source

@cat Certified is also accurate, but certificated is better since it covers all pilots who were at any time certified, whether they are currently or not. This includes those deceased, something very relevant to this discussion.

Ye link breaketh.

Pilots don't generally fly with their logbooks - partially for this exact reason, but also because they don't have to and it's additional clutter. So, in my case (and many Private Pilots), if I'm unlucky enough to fatally bend a plane then the investigators can simply grab my logbook from the flying club lounge.
In the case of airlines, I'm positive that they'll track hours in other ways - I doubt many airline pilots are going to fill in a small paper flying book after every leg of a journey (But I may be wrong!) nowadays. In terms of investigation, because of how important your flying experience is - many pilots also keep duplicate records - either by holding two books, photocopying or by electronic means. Even many casual General Aviation pilots will hold a physical copy and an online record.
Finally, record keeping in aviation is very important and it's normally possible for investigators to piece together information from incomplete sources. For example, a commercial company may know that Captain Jones had 3050 hours when he started, because they took copies for HR. Then, they could go through their aircraft records and add up the hours based on that.
It's also worth noting that just because the number sounds precise, it doesn't mean that the Captain of MH370 had literally 18,365 and no more. That's just the number that they can prove - he might not have logged all private flying, and maybe even some records have been lost but it's a number that's indicative of his experience.


text:
Is there a way to get descriptions of great circle routes?
Given that I am blind and love to know where I'm flying over, is there a online service that describes a great circle route in text form? e.g. in a format like this:

A great circle from CYVR to LTBA goes NNE over British Columbia,
  Alberta, Northwest Territories and Nunavut, passing over Arctic bay in
  the northernmost part of Baffin Island. Then across the middle of
  Greenland, crossing the Atlantic to Norway then Sweden, passing abut
  30 miles west of Stockholm. Then across the Baltic Sea and over the
  Kaliningrad Oblast, which is the small exclave of Russia that sits
  between Poland and Lithuania. Then across eastern Poland, western
  Ukraine, Romania, the very corner of Bulgaria, across the very western
  edge of the Black Sea and arrives in Istanbul from NNW.

(thanks to @TomMcW who left this in my previous question).
This way I can stop asking these great circle questions here.

How do you usually read maps ?

Have you tried using Google Earth to draw the great circle and make your own notes? The issue in any case is that the routes can vary significantly from the great circle to take advantage of winds. I've seen mid-course variations of over 1500 miles on long overseas flights.

I'm blind and i can't use google earth maps.  unless there's a tactile map that exists I can't read it.  and Hudson isn't always around to describe it to me, and I shouldn't have to always rely upon her.

@TheCat-alyst I have seen globes of earth that have the topography of the land on the surface that allows you actually feel the topography. You could identify the start and stop location on the globe and then trace with you hand and fingers a straight line and feel the continents and oceans and mountain ranges...etc. You may want more detail than this, but it could be very insightful. A physical globe is the best way for me personally to visualize great circle routes. Granted, its not very convenient to carry around.

I've seen references in two of your questions and you have me quite curious now. Who or what is Hudson (if I'm not being too personal)? You speak of "her" as though she's a friend, yet I get the feeling it is some sort of a device, instead.

I was wondering who, or what Hudson is too. I can't help but think of Tom Hanks' soccer ball, Wilson :)

@TomMcW and FreeMan Hudson is a friend of mine, she's originally from Manchester. She was the Hudson I referred to in my question regarding the flight between Manchester and Vancouver. She's good at trackign where we fly whe we travl together because her dream is to be a pilot herself.

@TheCat-alyst For your information, the Earth is NOT a perfect sphere.   It is like an old, dented baseball, hit hundreds and hundreds of times. Most globes (all that I know of) are spheres.  Most calculations use the Haversine formula, which treats the Earth like a sphere.  If you are talking military grade precision, you cannot use this approximation, favoring other much more complex math (there's half a dozen solutions, more or less complex and precise).  PS: 2D maps (Mercator maps) are NOT in proportion: Europe is displayed at a closer zoom level than other regions, like South America.

@tony gil Basically I am looknig for descriptions of where I would fly over, it doesn't have to be ultra precise, basically more like the description i cited above, though exact distances and directions aren't required. also keep in mind I'm bilnd and tactile globes don't show countries, they only show the topographical views.

@TheCat-alyst I pretty much thought so.  On the other hand, I am sure that my graphic explanation will give you a better idea ofwhat this lump of rock of ours occupies space.  As for Mercator distortions, the topography of Europe is easily identified. STEP 1: Find Africa.  STEP 2: Find the Mediterranean Sea above Africa.  Step 3: Everything North of that, basically constitutes Western Europe, the Balkans (you'll find a mountain ridge there, which is sort of the eastern boundary of Europe.  Bear in mind that Europe is not separate from Asia.


text:
What is the security policy for getting into a Control Tower in the US?
Are there any regulations the FAA has ruled to get into a Control Tower? Do people need any special kind of security clearance? Are there forbidden items or other special rules?
I'd also want to know if there's a way for non-pilots (your average civilian Joe) to get into a Control Tower.

Speculating: I read that if you're a licensed pilot, it should be fairly easy to arrange a tour. I'd be interested to know for a private individual though.

@DannyBeckett http://aviation.stackexchange.com/a/548/327 confirms your sayings

Ah yes, that is where I read it ;).

It is still possible (and in my experience not that difficult) to get FAA tower tours (and sometimes even TRACON or Center tours), though you should be reasonable in your expectations here -- You are probably NOT going to get a tour of the tower at JFK or LAX.

The FAA used to actively encourage pilots with an instrument rating (or pursuing instrument training) to sign up for ATC facility tours under a program called "Operation Raincheck" -- This program is still running, though it's been substantially scaled back (Poke around on the FAA Safety Team's SPANS system, or sign up for notices in your area and keep a sharp eye out. Tours usually have a very limited number of slots available, and they fill up fast!).
(As an example of how quickly the slots fill up, when N90 (New York TRACON) last had a Raincheck event it was full within a few hours of being announced. No, I didn't get a slot.)

At towered GA airports - particularly ones with a lot of flight training - you can also contact the tower directly. The printed AOPA Airport Directory has facility numbers in it but that's a little out of date. You can also get the phone number from Flight Service, the local FSDO, or ask the tower/ground controller for the number if they're not too busy.
When you call the facility explain that you're a pilot/student pilot and would like to arrange to tour the facility (and if possible shadow a controller). They will usually ask for your name, address, airman certificate number, and a few other things to run a check and get approval to let you in to the facility. You will also be expected to have government issued photo ID with you when you show up.

My experience arranging a tour of our local tower was extremely pleasant - they are happy to do the tours and let you shadow a controller, and I even got to pick their brains about some peculiarities in local procedures.
It's a great educational experience, and I would recommend it for any pilot/student pilot.

What about for non-pilots?

I'm wondering the same, @lnafziger

@lnafziger That is an excellent question.... that I've got no clue about - I didn't really become interested in what goes on in the tower cab until I had to interact with them :-) Can't hurt to call and ask though.

@voretaq7 Please do.

@Lnafziger, when setting up a tour "pilot" or "non-pilot" doesn't really come in to it. You need a photo ID and a pre-arranged appointment and that's about all. Note that non-US citizens should call several weeks in advance because that needs to be approved by people higher up in the FAA; a US citizen visit can theoretically be approved on the spot by the non-supervisory "controller in charge" but will more likely be routed to the facility manager for approval.

As @voretaq7 says, getting tours of LAX of JFK towers just won't happen unless you happen to fly for an airline with a base there and/or are good at persuasion.  I've tried to negotiate a tower tour with the supervisor at LAX on short notice but he did indicate if I had a lot of lead time they might have been able to work something out.
The easiest way to get a tour in my experience is just to call and ask for someone to talk to to request a tour.  I've been in the tower cab at EWR, AUS and CRG and in the Austin TRACON.  All of those were arranged with a phone call, a social security number and proof of citizenship (all post 9/11).  It helps to mention you  are a pilot and want to see how things work on their side.
Typically the tower guys are going to want at least one of you to be a pilot and they'll want more lead time if you are bringing a group.  They'll also probably want to verify citizenship for everyone ahead of time and you'll want to be up front if you have an non-US people in the group just so they don't get surprised when you show up and they ask for passports or other ID.  Bring donuts.
I have also toured the San Angelo, TX FSS.  For those guys I was already on field and just called the briefing number and asked if I could walk over.  They were happy to have us (I had a student with me).
If you want a tour of any facility, just call.  They'll tell you what they require and how and when the tour will happen and who you can bring.

+1 for "bring donuts"

I've arranged tours of two control towers (a class D and a class B) and a TRACON without any issues. I was only required to provide proof of US citizenship, from what I remember.
You must turn OFF (not airplane mode) cell phones before entering the tower or active part of the TRACON.


text:
AIP, AIC, NOTAM, ANO (UK): How do they relate to Annex 15 of Chicago Convention?
I've recently started studying for my Air Law and Meteorology exam and am trying to get my head around some of the basic literature / legal documentation structure.
As I understand it the Chicago Convention outlined a series of ICAO Articles that are available in detail as Annexes. These are introduced into law in the UK via the Air Navigation Order.
I'm having some confusion understanding the AIP and how this relates back to the ANO, if at all. Not only this but also what the main differences between an AIP, AIC and NOTAM are.
Is anyone able to help by concisely explaining how these entities relate to one another and how they differ so that I can build a mental image before studying each further, I would greatly appreciate it.

I did read that before asking, It didn't really help explain the place of each from a rookie point of view.

Annex 15 of ICAO Chicago convention describes the required information for safe conduct of flights, and which aeronautical information is to be provided by ICAO members. Each country needs to provide an aeronautical information service (AIS) in a standardized form, comprising static and dynamic data.

Static: Aeronautical information publication (AIP), AIP amendments and charts. AIP is generally updated each 28 days.
Dynamic: Notam, AIP supplements.

Explanatory information doesn't fit well in the previous categories, and is grouped in aeronautical information circulars (AIC).
Details

AIP: Authoritative information issued by an ICAO member containing long lasting aeronautical information essential to air navigation.AIP list by country.
AIP amendment:  Permanent change to AIP.
AIP supplement: Temporary change to AIP.
Notam (and Snowtam): Notice distributed by a telecommunication system, concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations. Also associated with Notam: pre-flight information bulletin (PIB), a presentation of current Notam information of operational significance, prepared prior to flight.Notams in US.
AIC: Information that doesn't qualify for inclusion in AIP or Notams but which relates to flight safety, air navigation, technical, administrative or legislative matters. This could include mid-term prevision for changes in the regulatory or technical frameworks, results of safety investigations, scientific discovery related to how weather impacts aviation...List of Canada AIC.

Full aeronautical information contains:

AIP, including amendments
Supplements to the AIP
Notams
AIC
Checklists and lists of valid Notams.

Source for the above definitions: Manual of Aeronautical Information Services, India.
Regarding The Air Navigation Order (ANO), specific to UK

"On 7 December 1944, the majority of the world's nations became
  signatories to the "Chicago Convention", the aim of which was to
  assure the safe, orderly and economic development of air transport.
  ICAO sets out, in the terms of the convention, the rules, regulations
  and requirements to which each signatory must adhere. The Civil
  Aviation Act 1982 is the UK's means of discharging its ICAO
  responsibilities. This legislation required the creation of the CAA.
  The Air Navigation Order (ANO) is the law that empowers us to carry
  out our duties."

Source.
ANO is the legal framework valid for UK, to empower aeronautical agencies and their publications, in accordance with Annex 15.